Combined seat and backrest unit



FIG. 1 is a front and side perspective view of a combined seat, and backrest unit embodying my new design;

FIG. 2 is a back and side perspective view of the combined seat, and backrest unit of FIG. 1;

FIG. 3 is a side elevational view of the combined seat and backrest unit of FIGS. 1 and 2; and

FIG. 4 is a top plan view of the combined seat and backrest unit of FIGS. 1 through 3. 

The ornamental design for a combined "seat and backrest unit", substantially as shown. 